Commutator for dynamo-electric machines.



My WALKER.

COMMUTATOR FOR DYNAMO ELECTRIC MACHINES.

APPLIGATIQN FILED FEB. 2, 1907.

949,103. Patented Feb 15,1910.

WITNESSES:

W ATTbRNEY ANDREW a GRAHAM C0,. Paow-unmuupnzns. wnsumcmn. 0. c.

INVENTOR UNITED STATES PATENT OFFICE.

MILES WALKER, OF MANCHESTER, ENGLAND, ASSIGNOR TO WESTINGHOUSE ELECTRIC& MANUFACTURING COMIANY. A CCRPORAT'ION 0F PENNSYLVANIA.

COMMUTATOR FOR DYNfZtMO-ELEOTRIC MACHINES.

Specification of Letters Patent.

Patented Feb. 15, 1910.

To all whom it may concern.

Be it known that 1, MILES Wamtnn. a sub ject of the King of GreatBritain, and a resident of Manchester, in the county of Lancaster,England, have invented a new and useful Improvement in Gommutators forDynamo-Electric Machines, of which the following is a specification.

My invention relates to commutators for dynamo-electr1o machines, and,it has particular reference to such commutators as are adapted for usewith machines which are driven at high rates of speed.

In operating dynamo-electric machines at very high speeds, considerabledifficulty has heretofore been experienced in collecting currents bymeans of cylindrical commutators on account of the difliculty ofmaintaining the brushes in contact with the cylindrical surfaces. Toavoid such di'liiculty, ithas been proposed to so locate the brushes atthe end of the commutator, that they shall make contact with a planesurface provided for thatpurpose. Such arrangement has been foundsuccessful to some extent, as the vibrations of a shaft longitudinallyare generally not very rapid, but the surface provided for collectingthe current is limited and, consequently, is not suitable for dealingwith large currents unless the diameter of the commutator is made verygreat, which is obviously objectionable, for many reasons. It has alsobeen proposed to cut grooves in the commutator cylinder and to press thebrushes partly against the inclined surfaces and partly against thecylindrical. face. This method has been only partially successful, asitdoes not prevent chattering of the brushes when the commutatorcylinder is slightly unsymmetrical. Another difficulty which has arisenin connection with cou'nnutators intended for operation at high speedshas been to so design them as to enable very large currents to becollected without making the commutator cylinders of unwieldly length.The diameter is limited by the permissible peripheral speed, so that thenecessary space for the brushes and the necessary cooling surface has tobe provided by increasing the length. Moreover, when steel shrink ringsare added to hold the commutator segments together, the length is stillfurther increased by the combined width of the rings and by thenecessary insulating space between the brushes and the rings.

.Brccording to the present invention, I avoid the difficulties abovementioned by providing the commutator cylinder with annular peripheralgrooves which are substantially rectangular in cross section and of adepth and width sniiicient to contain brush holders provided withbrushes to press against the plane radial faces of the coininutatorbars, thus provided. Since the brushes make contact with the side wallsonly of the grooves, and vibrations of the commutator cylinder aremainly lateral, substantially all interruption and variation of contactbetween the brushes and the cooperating surfaces is avoided. In thebottoms of the grooves l place metal bands which are insulated from thebars and are firmly secured in place to hold the bars in position. Thebrushes are preferably of carbon and very short, being provided withsprings to press them in an axial direction against the plane faces ofthe comn'nitator bars. Each of the annular grooves is prefcrably madewide enough to contain two brushes, disposed end to end, so that bothsides of the grooves may be utilized for collecting the current.

In the accompanying drawings, Figure l is a part sectional sideelevation of a commutator cylinder constructed in accordance with. myinvention. Fig. 2 is a part sectional view of a modification of a detailof Fig. 1.

Referring to Fig. l, the commutator cylinder comprises a number ofsegments 1, notched as indicated, so that, when assen bled, a series ofannular peripheral grooves 52 is formed having plane radial faces 3against which brushes i are held under pressure acting in a directionparallel to the axis of the commutator cylinder. The brushes l consistof blocks 5 of carbon which are supported in holders 6 pivotally mountedupon a carrier (not shown) in any appro priate way and acted upon bysprings, in the usual manner. The blocks 5 may be of rectangular form orthey may conform more or less to the outline of the cross section of theindividual commutator segments. The widths of the grooves 2 maybe onlysufiicient to accommodate one row or ring of brushes but, as ispreferred, may be of such width as to allow two rows or rings of brushesto be located therein, end to end, one row or ring of brushes actingagainst one wall of the groove and the other row or ring of brushesacting against the opposite wall. By reason of this construction, alarge surface is afforded for current collection and also a largesurface for the dissipation of heat, while, at the same time, the lengthof the commutator, for a given capacity, is lessened. The commutatorsegments 1 are secured by split or transversely separated rings 10 ofchannel section located in the bottoms of the grooves 2-, in conjunctionwith retaining bands 11 composed of turns of suitable wire, such as harddrawn steel wire, which are tightly wound on after the ring sectionshave been placed in position. Bands 8 of insulating material aredisposed between the rings 10 and the bottoms of the grooves 2 and, as afurther precaution, similar insulating bands 12 are arranged to surroundsaid rings 10 in order to prevent I short circuits by reason of carbonor other dust particles. As a modification of this form of commutator,the bottoms of the l grooves 2, in lieu of being parallel to the axis ofthe machine, may incline slightly toward the one or the other endthereof, as shown in Fig. 2, so that each resembles the surface of atruncated cone. After this surface has been insulated, the dividedchannel-section ring 10 is placed in position upon a portion thereofwhich is nearer the end of smaller diameter, as illustrated to the leftof the figure, and the wire of the band 11 then wound on. Thereafter,the ring 10 and the band 11 are expanded by heat and the whole displacedtoward the end of the aforesaid surface which has the larger diameter,as illustrated to the right of the figure. When cool, the ring and bandcontract. and tighten upon the insulating band 8 so as to prevent thecommutator segments from working loose.

Obviously, although the securing bands have been shown as applied to allgrooves of the commutator, they need not necessarily be so, as the samemay be reduced in number if desired.

I claim as my invention:

1. A commutator cylinder comprising insulated commutator bars and havinga series of relatively deep peripheral grooves the side walls of whichconstitute plane contact surfaces, and clamping bands located in thebottoms of said grooves to hold the commutator bars againstdisplacement.

2. A commutator cylinder having peripheral grooves the side walls ofwhich constitute plane radial contact surfaces, and insulated clampingbands located in the bottoms of a plurality of said grooves.

A commutator cylinder having peripheral grooves the side walls of whichconstitute plane contact surfaces, layers of insulating materialdisposed on the bottom surfaces of said grooves, and clamping bandssurrounding said insulating layers.

et. A commutator cylinder having a plurality of peripheral grooves thebottom surfaces of which are of slightly frusto-conical form, layers ofinsulating material disposed upon said bottom surfaces, and clampingbands surrounding said insulating layers.

5. A commutator cylinder having peripheral grooves the site walls ofwhich constitute contact. surfaces, and insulated clamping bands locatedin the bottom of some or all of said grooves.

In testimony whereof, I have hereunto subscribed my name this 16th dayof January 1907.

MILES lVALKElt.

\Vitnesses J. C. Bon'rrnowna, G. BoUTrLowER.

